In all three cases I find the original PDFs more pleasant to read. HTML typography is not up to snuff. I read them on a laptop, however, and I can see that this would be useful if one is forced to read on a phone.
(One thing that is very ugly in the PDFs, and most scholarly papers, is the use of different-colored boxes for hyperlinks. Authors, please consider putting
For me the PDF was fuzzier https://imgur.com/a/WJ5y3 and the HTML version was more convenient to read in a single column. The two-column format is nice if I'm skimming to see if a paper is going to be interesting, but when I sit down to read it the HTML version definitely wins.
(One thing that is very ugly in the PDFs, and most scholarly papers, is the use of different-colored boxes for hyperlinks. Authors, please consider putting
\usepackage[colorlinks]{hyperref}
in your LaTeX preambles.)